Long-term outcomes of a phase II trial of moderate hypofractionated image-guided intensity modulated radiotherapy (IG-IMRT) for localized prostate cancer

Abstract

Purpose: To evaluate long-term radiation toxicity and biochemical control of two moderately hypofractionated radiotherapy regimens for prostate cancer.

Material and methods: Eligible men with localized prostate cancer received image-guided intensity modulated radiotherapy (IG-IMRT) to a dose of 60 or 66Gy in 3Gy fractions in a phase II trial. Endpoints included late gastrointestinal (GI) and genitourinary (GU) toxicity and biochemical failure (FFBF).

Results: Ninety-six men received 60Gy and 27 received 66Gy. Accrual to the 66Gy cohort terminated early due to excessive Grade 3-4 late toxicity. Median follow-up was 128months (60Gy) and 108months (66Gy). In the 60Gy cohort, cumulative late Grade ⩾2 GI and GU toxicity at 8years was 4% and 12% respectively. In the 66Gy cohort, late Grade ⩾2 GI and GU toxicity was 21% and 4% respectively at 8years. The 5- and 8-year FFBF for 60Gy was 81% and 66%, and for 66Gy was 88% and 80%.

Conclusions: Moderate hypofractionation with IG-IMRT to 60Gy was associated with favorable late toxicity although late urinary toxicity and biochemical failures were observed beyond 5years. Dose escalation to 66Gy was associated with significantly worse late toxicity.

Keywords: Hypofractionation; Late toxicity; Outcomes; Prostate cancer; Radiotherapy.